555 timer

[audioguru]

An ordinary IRF540 Mosfet needs a gate voltage of 10V or more for ALL of them to turn on well.
A few might turn on with a gate voltage of only 6V. You might find one if you test hundreds of them.
A logic level Mosfet is GUARANTEED to turn on well with a gate voltage of only 4.5V or more. Order one.

Why do you pay $40.00 for shipping? Do you live on the moon?

 

[Maverick28]

Well old mate at uni who would claim to have discovered MOSFETs say the IRF540N, they will turn on no doubt at 4V. I called BS but he assured me the 40 years of his experience they were fine, so looks like the question is now is how many V's my motor will handle.

the land of Oz, about as arid as the moon.

 

[audioguru]

="Maverick28, post: 1147438, member: 250826"]Well old mate at uni who would claim to have discovered MOSFETs say the IRF540N, they will turn on no doubt at 4V. I called BS but he assured me the 40 years of his experience they were fine.

Why don't you believe the datasheet from the manufacturer?
Some IRF540 Mosfets will be barely turned on (actually they will be almost turned off) with a gate voltage of only 4V. They are guaranteed to work well when the gate voltage is 10V.

 

[Maverick28]

audioguru Dont worry i had that argument with him and he assured me it would! Im on your side don't worry haha. So is it possible to grab a 10-12V Dc adapter and run the motor of that somehow without damaging it?

 

[audioguru]

So is it possible to grab a 10-12V Dc adapter and run the motor of that somehow without damaging it?

We do not know if the 6V motor will burn out when powered from 10-12V.

 

[ericgibbs]

Dont worry i had that argument with him and he assured me it would! Im on your side don't worry haha. So is it possible to grab a 10-12V Dc adapter and run the motor of that somehow without damaging it?

hi M,
If you use the 7.5V 2A power supply and connect it as I said in my previous post, it will drive your IRF540 and motor.

Try it and if it does not work with a Vgs of 7.5V , I will buy you a pint.

E

 

[Maverick28]

**broken link removed**

which one should i be using? E?

thanks!

** This could be a silly question but for the diode (1N4001) it is only rated for 1A.? is this okay?

**broken link removed**

 

[ronv]

You can use the 16 volt cap.
The 1N4001 is ok for the diode across the motor, but the one in series should be like a 3 amp one. Something like an MURS320.

TheFR302 from Jcar would work.

 

[ericgibbs]

hi M.
Follow 'ronv' s advice.
E

 

[Maverick28]

E! i accidentally left the power adapter (7.5V/2A) at the farm, i do however have a 7.5V 1.5A one here. i cut it open and measured its Volts. and the output was something like 11.2. On the sticker it quotes 7.5A 1500mA 11.25VA. im thinking im ready the VA value? will this be okay for my scummy motor? i ran it quickly and it worked but its pumping along pretty quick... Once i get it integrated into the circuit will this eventually die down?

 

[alec_t]

7.5V (when the adapter has the 6V rated motor as a load) will over-drive the motor by 25%. It will probably get hot. Using the FET to switch it on continuously will make very little difference to the power it's dissipating. It won't 'eventually die down'.

 

[ericgibbs]

E! i accidentally left the power adapter (7.5V/2A) at the farm, i do however have a 7.5V 1.5A one here. i cut it open and measured its Volts. and the output was something like 11.2. On the sticker it quotes 7.5A 1500mA 11.25VA. im thinking im ready the VA value? will this be okay for my scummy motor? i ran it quickly and it worked but its pumping along pretty quick... Once i get it integrated into the circuit will this eventually die down?

hi M,
Did you have the 3Amp diode in series from the 7.5V supply to top as the motor as I stated previously.?
Off Load some of the cheaper power supplies will have a higher than expected voltage.
E.

 

[audioguru]

I have a cheap 9VDC adapter that measures 18VDC with no load. It produces exactly 9VDC with its rated load but then it gets very hot.

 

[Maverick28]

Alright.! I built that bad boy. all done. @ E and everyone else thankyou for your generous contribution. Really appreciate the help.

NOW next problem, any of you LADs here, who is good with OP amps. Just a quick question, you know how when you by a OP amp they have like 8 pins or something. My shematic is only asking for me to use the + - and out put pin. What do i do with the rest of them? **broken link removed** heres my OP AMP . I could only buy the TL084. It has two opamps inside of it. !

 

[audioguru]

you know how when you by a OP amp they have like 8 pins or something. My shematic is only asking for me to use the + - and out put pin. What do i do with the rest of them?
Here is my OP AMP . I could only buy the TL084. It has two opamps inside of it. !

No.
The datasheet shows that the TL084 has 14 pins and has 4 opamps inside. If you do not use all 4 opamps then the unused ones must be disabled properly.
Pin 4 is VCC+ and is connected to the positive wire of the power supply. Pin 11 is VCC- and is connected to the negative power supply or 0V if there is only a single-polarity supply.

 

[Maverick28]

Here is the schematic. SO is there anyway to disable the other 3 OpAmps?

** they were sold out of the TL082!!

***I guess i could use two OA and disable the other two?

 

[audioguru]

There are thousands of dual opamps available in the world. Use one.

Your opamps circuit does not have a power supply so it will not work.
The reference voltage is 2.5V so maybe the power supply is 5V? But the MINIMUM supply for a TL082 or TL084 is 7V and then its output voltage swing is not much.

I increased the values of the resistors.

 

[Maverick28]

i'm stuck with this one. how to disable the other two O-amps?

 

[audioguru]

An opamp has extremely high gain so you do not want one floating because it might oscillate and cause interference. To disable it connect its (-) input to its output making it have a gain of 1 then bias its (+) input at half the supply voltage with two resistors making a voltage divider. One voltage divider can feed many opamps.

What is your supply voltage for the opamps? A TL084 need a MINIMUM of 7V.
The circuit you posted needs a dual-polarity supply because the inputs of a TL084 must not be within 4V from the negative supply voltage which is 0V if the supply is a single positive voltage. Also the output cannot go within about 3V from the supply rails.

Why are both inputs +2.5V with no signal?

 

[Maverick28]

Hey I'm going to move this topic into its own thread to save confusion, i left out some detail in my circuit as well! It involves a solenoid !! sorry ahha